Volkswagen Crafter vibrates

[lastvagn8]

Hello all,
Need some helpful insights.
VW Crafter MY 2018 AllDrive (AWD) 4 cylinder diesel. Tires 265/60R16C 70000 kms

Vibrates while accelerating/under load. People at workshop checked the propshaft, the universal joint felt stuck. So since it wasnt any spareparts for the axle, the entire prop.shaft was replaced.
The time the prop,shaft was removed the vibrations were gone, supporting the theory.
Eventually the new arrived, mounted and the vibrations returned.

This is when I was called in to help diagnose. Cant find or feel any faults with bushings, alignment, or bearings.
When driving there is almost a burring sound, but foremost a vibration.
There is a T1, T2 as shown in the attached files. After the first drive, the tires were removed and balanced at the tireshop. Cant see there is a difference.
Checked the oil in the Haldex-coupling kind of darkgrey only 10000kms old (replaced at 60 000kms) drained the rearaxle, oil was good colour, but the magnetplugs were stuffed with fine filings. No bigger parts at all.

But I notice a 4:th engine vibration during test run? Togheter with the T1/T2
Trying to figure this out, can there be a dualmass flywheel that is the failing component. Thinking it takes more torque when prop.shaft is attached again?

Thankful for any feedback!

[Steve Smith]

Hello and thank you for the post

Given the symptom has cleared (i.e., no vibration) with the propshaft removed, we must focus on this golden nugget

Consider not only the propshaft, angles, alignment, and “whip” but also transmission output and differential input/output

I have several questions that I hope you can clarify?

In the image below (at approx. 100 km/h) we have the engine and road speed increasing suggesting the engine and drive train are under “load” however, the greatest offending vibration is T1
Could you confirm if this capture was taken with the propshaft removed and before the wheel balance?

Image 1

In contrast to the above, note below during similar driving conditions we have an unknown Vertical vibration at 148 Hz which appears to be linked to road speed and “load” (Load being the primary factor causing our vibrating force)

Image 2

Can you confirm the accelerometer was placed in the vertical orientation with the screw thread facing forward?

If so, we can confirm the axis of vibration to in the vertical plane

Can you confirm the peak we have captured above (148 Hz) appears when you can hear/feel the vibration? (This is vital to the diagnosis)

I say hear/feel because frequencies between 20 and 200 Hz are interpreted by humans using differing senses (depending on the individual)

I have exported the data and listened to the audio from the accelerometer and I can hear a booming noise but I cannot be 100% that this is our customer complaint

See here for audio exports of NVH data viewtopic.php?p=98084#p98084

Drilling down further in the above capture, we can see how the 148 Hz vibration appears shortly after an upshift (The engine rpm drops from 2638 rpm to 2186 rpm and P1 is rotating slightly faster than E1 suggesting we are in an “over-drive” state

Once again, if the 148 Hz is our offending vibration, what conditions occur on the vehicle during this scenario? We have an upshift yet the vehicle continues to gain speed suggesting once again “load” is placed on the drive train

See below for the 3D view of the above capture which helps with the perception of vibration over time

Image 3

I am not familiar with the Haldex system but it certainly cannot be ignored as it will influence the transmission of power from the engine to the rear road wheels

You also mentioned dual mass and E4 which again cannot be ignored (see below)

Image 4

Does the vehicle exhibit any other “typical” dual mass symptoms? i.e., knocking during start up, judder when pulling away, "feel" of a misfire or “clatter” noise during cranking etc.?

70,000 km is very low for a dual mass failure unless of course the vehicle has had a hard life?

E4 is four disturbances for one revolution of the engine or a component rotating at 4 times engine speed (148 Hz x 60 = 8,800 rpm)

Just thinking this through, is it possible to drive this vehicle with the propshaft installed but the Haldex unit electrically disconnected, such that “drive” cannot pass through into the differential?

This may help narrow down the area of interest along with placing additional accelerometers along the drive train. (Keep the vertical axis in the cabin as a reference and measure the vertical axis of additional accelerometers placed at strategic points of interest along the rear drive line)

Forgive my lack of product knowledge

I hope some of this helps, take care……Steve